The subject matter disclosed herein relates to wireless communications, and more specifically to automatic re-alignment of antennas.
Antennas are used for a wide variety of communication applications. One of the more recent applications for antennas has been for wireless communications in the 57-64 gigahertz (GHz) industrial, scientific, and medical radio (ISM) band. This band is license-free under the ISM structure and offers 7 GHz of continuous spectrum. In addition, license-free 60 GHz millimeter wave communications may present operational advantages such as narrow beam width and oxygen absorption for interference immunity, privacy, and gigabit-plus data rates. However, at 60 GHz, a small antenna aperture or effective area can provide small beamwidth, which can entail operational problems if misalignment of an antenna occurs (e.g., offset or misalignment of antenna boresight). For example, a parabolic dish antenna with a diameter of only 10 centimeter (cm) and an efficiency of 0.65, exhibits a half-power beamwidth of about 3.4 degrees, and a change in this antenna's boresight of only 1.7 degrees would result in a drop of 3 decibels (dB) of power sent in the original direction. Such a situation is present in the use of 60 GHz communications where the antennas are mounted on structures that are subject to angular movement (e.g., antennas mounted atop utility poles or street lighting poles that sway, deflect, or vibrate when subjected to wind and/or other external forces). Traditionally, antenna alignment methods were developed based on beacons and/or a received signal strength indicator (RSSI). However, these techniques may be process-intensive and may not operate properly due to the need for a feedback link that is not present or other conditions. Accordingly, it is now recognized that it is desirable to provide systems and methods for antenna alignment independent of beacons or RSSI.